Our Garden: Winter care of fruit trees

Winter is a time when our gardens and trees go into dormancy, but that doesn't mean our chores are done. Most deciduous fruit trees, says Contra Costa Master Gardener Terry Lippert, will need to be pruned and some will need treatment for insects and diseases.

Now is a bit early for pruning, Lippert told the audience at Our Garden on Wednesday, but other things need to be done. Here's her advice for winter care of deciduous fruit trees.

Clean up

Remove all fruit mummies -- rotted or dried fruit -- from the tree. The fruit can harbor insects and disease.

Rake and thoroughly clean up leaves and other debris beneath trees.

If you had a serious insect or disease problem this year, dispose of debris in the green-waste bin. If you had healthy trees, you can add it to your compost bin.

Pruning

Most deciduous trees -- those that drop their leaves every year -- are best pruned during their dormant stage.

Trees are dormant from December through early February, but it is OK to prune any time after all the leaves have fallen.

The exception to winter pruning is apricots and trees in the apricot family, such as pluots and apriums. Pruning them when it is wet and damp risks having the Eutypa infection. Apricots and their relatives should be pruned in August.

Follow the Five Ds of pruning: Remove dead, dying, damaged, diseased and deranged limbs and branches.

Also remove water spouts -- branches that grow straight up -- and root suckers.

Spraying

Some trees may need to be sprayed for disease and insect infestation.

Scale is usually kept in check by beneficial insects that prey on the tiny insects. If you have a serious infestation, however, you may need to use a horticultural oil. The oil doesn't contain insecticide. It simply smothers the scale. You can spray during the dormant season or in early spring when the young, called crawlers, emerge.

Mites are another problem that can be bothersome in fruit trees. Beneficial insects should keep them under control, but if the infestation is severe, you can use horticultural oil.

European red mites should be sprayed during delayed dormancy -- early February when the buds are swelling -- but not yet broken. Pear blister mites can be sprayed after harvest, from late October to November.

Horticultural oil can be used to kill aphid eggs in the early spring. In plums, aphids should be sprayed after leaves have fallen in early November.

If you haven't had a problem with insects, don't worry about spraying.

Peach leaf curl must be treated every year if the tree has shown signs of infection in the past. The tree should be sprayed twice a year, once in December after leaf drop and again in February before the tree flowers out. Spray only when there is no forecast of rain for four or five days. Use a copper fungicide and add 1 percent horticultural oil to help the fungicide stick to the tree.

Bare root

Winter is a good time for buying and planting bare-root fruit trees.

Start training the tree immediately after planting, pruning to shape.

Pruning guidelines

Here are some pruning tips for some common trees.

Apricots

Don't prune in the winter; that way, you can avoid a common infection spread by rain and damp weather.

If you've had significant fruit loss from brown rot, consider applying fungicides before the rains begin.

Cherries

Prune in the summer, thinning about 10 percent of wood that grew in the prior season.

If you had significant infestations of scale, mites or aphids, spray with horticultural oil before bud break.

Peaches and nectarines

Prune after leaf fall, removing about 50 percent of new wood.

Remove mummified fruit to reduce the risk of brown rot.

Spray for peach leaf curl if there is a history.

Plums

Prune after leaf fall, removing about 20 percent of new wood.

Remove mummified fruit to reduce the risk of brown rot.

If you had significant infestations of scale, mites or aphids, spray with horticultural oil before bud break.

Pomes (apples, pears, quince)

Prune after leaf fall, removing about 10 percent of new wood.

Remove any remaining fruit on the trees to reduce the risk of codling moth and scab disease.

If you had a significant problem with scab disease, consider spraying with fungicide just before bud break. A second application may be needed two weeks later and a third application after most of the petals have fallen.

If you had significant infestations of scale, mites or aphids, spray with horticultural oil before bud break.

About Our Garden

Free gardening classes are offered 10-11 a.m. Wednesdays at the garden, Wiget Lane and Shadelands Drive in Walnut Creek. Master Gardeners also are available to answer questions at the Help Desk; plants, seeds and worm compost also are available for sale most weeks.

Next time: "Perennial Vegetables," with Janet Miller and Helen Erickson